The present invention relates to a processing apparatus for subjecting an object, such as a semiconductor wafer or an LCD substrate, to processes of coating, development, etc.
A process for fabricating a semiconductor device includes a series of steps of applying a treatment liquid such as a photoresist liquid to a semiconductor wafer represented by a silicon wafer, exposing a film of the photoresist liquid with a circuit pattern, etc. reduced in size by means of photolithography techniques, and developing the photoresist film.
The above-mentioned coating/developing process system comprises, as an integrated structure, a cassette station for carrying a semiconductor wafer, as an object to be processed, into/out of a cassette; a washing unit for washing the wafer; an adhesion unit for dehydrating the surface of the wafer; a cooling unit for cooling the wafer down to a predetermined temperature; a resist coating unit for coating a resist liquid on the surface of the wafer; a baking unit for prebaking or postbaking the wafer prior to or following the coating of resist liquid; a peripheral exposure unit for removing a resist portion from a peripheral area of the wafer; a wafer transfer table for transfer of the wafer to/from an adjacent exposure device; and a developing unit for applying a developing liquid to the exposed wafer and selectively dissolving a sensitized or non-sensitized portion in the developing liquid. Thus, the manufacture of the semiconductor device is efficiently carried out.
In this type of process system, a wafer transfer path is generally provided at a central part of the system in the longitudinal direction. The respective units are disposed on both sides of the transfer path, with their front sides facing the transfer path. A wafer transfer device for transferring wafers to the respective units is provided movable over the wafer transfer path. Since the system has a laterally elongated structure wherein various process units are arranged along the horizontally extending wafer transfer path, the space for installation of the system is great, resulting in a high cost of the clean room. In particular, if the cleanness of the entire system or respective parts is to be enhanced by a vertical laminar flow method that is applicable effectively to this type of system, the initial costs and maintenance costs of an air-conditioner, a filter, etc. increase due to the large space.
Jpn. Pat. Appln. KOKAI Publication No. 4-85812 proposes a process system wherein a wafer transfer device is disposed to be movable vertically and rotatable about a vertical axis, and process units are provided in multiple stages around the wafer transfer device.
According to this process system, the space for installation of the system is reduced and accordingly the cost for the clean room is reduced. In addition, the speed of transferring and accessing wafers is increased. Thus, the throughput in this system increases.
In this type of process system, however, wafers are subjected to predetermined processes in the process units arranged in multiple stages and consequently the condition of clean air fed into the process system, e.g. the quantity, temperature and/or pressure, may vary. If the condition of air within the process system varies, proper processing cannot be carried out, with the result that the process performance and yield will lower. In particular, since the space for movement of the wafer transfer device is substantially sealed, the air containing particles produced from a wafer transfer device driving unit is compressed at upper and lower end regions of the space for movement, dispersed, and let to flow into the respective peripheral units. Consequently, the yield of semiconductor devices deteriorates. In particular, when the transfer device is rotated, a great deal of particles are produced and this problem becomes more serious.
If the air fed into the process system is discharged after processing, particles or contaminants such as amine produced within the process system are brought into the clean room. As a result, the cleanness as well as the life of the clean room decreases. Further, if organic contaminants such as amine are present within the clean room, such contaminants will adversely affect other processing apparatuses within the clean room, e.g. a CVD apparatus for forming a thin film.